1. Field of the Invention
The present invention relates to auxiliary cutter units of a shield machine.
2. Prior Art
A prior art shield excavator for excavating earth, stone or other materials (hereinafter referred to as soil) for forming a tunnel is provided with a cutter head which is disposed at the front end of a shield body and is rotated by a cutter head motor and to which a plurality of cutters are attached.
The cutters are normally detachably attached to a front surface of a face plate of the cutter head by fixed members such as bolts and are replaceable with new ones when they are broken or worn away during excavation.
When the cutters are broken or worn away during the excavation, an operator enters between the cutter head and a working place and replaces the broken cutters with new ones. However, there are drawbacks that it takes much time for replacement, which leads to the extension of a term of construction work, and it involves a danger that the working place collapses and is deluged since the working place is under inferior working condition.